Alternating current (AC) power provided by commercial electric utility generators frequently is subject to random disturbances and “brown outs”. These events can cause malfunctions in electrical equipment operating from AC line voltage, such as the standard 50/60 Hz power provided in the United States.
AC line voltage regulator devices are used as a buffer between the utility AC power line and sensitive electrical equipment to eliminate or reduce voltage variations in the power supplied to such electrical equipment. Conventional AC line voltage regulator devices differ in design and operation. Some devices offer an AC inverter output stage with amplitude and frequency adjustments. Other AC regulators use a Ferro-resonant transformer with an inductive capacitive (LC) tank (SOLA) to maintain a relatively stable output at a fixed line frequency without adjustment. Other devices use variable auto-transformers and a motor drive to adjust the voltage amplitude compensating for variations in the AC line voltage. This latter is a voltage boost device, which incorporates a transformer with a tapped winding and switches for changing the turns ratio, which can increase or decrease the variable line voltage.
While the existing line voltage regulator devices do provide a functional service in many applications, relatively high cost, large size and weight, along with performance shortcomings exist. It is desirable to provide an improved AC regulator circuit which overcomes the shortcomings of the currently available AC line voltage regulator devices.